1. Field of the Invention
The present invention relates to a method for fabricating a hydrogenated silicon oxycarbide (H:SiOC) thin film, and in particular to a method for fabricating a hydrogenated SiOC thin film having low dielectric permitivity, which is capable of minimizing carbon loss although a thin film passes a following process such as an oxygen ashing, etc.
2. Description of the Prior Art
With the intergration of semiconductor device, because finer circuit structure is required, a horizontal interval between metal wiring formed on the same plane has to be reduced. However, when an interval of metal wiring is reduced, cross talk may occur between the metal wiring by a parasitic capacitance between them. In that case, an electric signal transmission through the metal wiring may not be performed well or transmission speed may be lowered. In order to improve a speed of signal transmission through the metal wiring, the parasitic capacitance between the metal wiring has to be low. Accordingly, insulating layers having low dielectric permitivity are required.
One of the insulating layers, a SiOC (silicon oxycarbide) thin film fabricated by retaining lots of carbon in the conventional SiO2 thin film comes to the front. The SiOC thin film can be formed by a CVD (chemical vapor deposition), herein, methylsilance, di-methylsilane, tri-methylsilane and tetra-methylsilane, etc. can be used in the CVD.
In the SiOC thin film, carbon retained in the thin film as CHn shape dangles about part of SiO2 having a mesh structure, and air hole having a nanometer size is formed by the dangling, herein, the air hole affects dielectric permitivity lowering. In addition, it is assumed that Si—CH3 bonding has smaller ionic polarizability than that of Si—O bonding, however, its mechanism has not been clarified accurately.
However, in the SiOC thin film, because an ashing process using oxygen is performed to eliminate a sensitizing solution hardened by a dry etching, a wet etching or an ionic injection, etc. and carbon loss in the thin film occurs by an additional following process, thin film characteristics may be lowered.